A notebook computer is excellent in portability, but is illegally carried away to the outside very easily. As the computer use has become sophisticated and versatile in recent years, a user increasingly tends to store important information in the computer, and if the computer is stolen, the loss of information resources by leakage becomes larger as compared with the loss of the physical resources of the computer.
Published Unexamined Patent Application Nos. 8-50690 and 10-124764 disclose an electronic article monitor system using a non-contact communication technique called an RF (Radio Frequency) transponder system. The RF transponder system commonly includes an exciter/reader or ER, and an RFID transponder or an RFID (Radio Frequency Identification) tag. An RFID tag is attached to an article in an area to be monitored, and an ER is placed at the gate of the area to continuously generate an RF exciting signal. When the article having the RFID tag approaches the gate, the ER sends the exciting signal to give power to this, so the RFID tag itself does not need particular power for operation. Upon receipt of the RF exciting signal, the RFID tag generates an identifier code and other data signals, and sends them back to the ER as a response signal at a specified frequency. When the ER detects the identifier code included in the response signal, it gives an alarm sound to prevent the theft of the article at need. To carry the article away from the monitoring area without sounding an alarm, it is needed to set the RFID tag to a state of not sending an alarm signal, or to remove it.
Published Unexamined Patent Application No. 5-35354 discloses a technique for preventing a notebook computer from being stolen. A notebook computer is provided with antitheft means for detecting changes in the setting statuses such as amount of setting tilt, setting pressure, and setting distance, and means for raising an alarm in response to changes in the setting statuses. The computer continuously monitors the setting statuses when these means are ready to exhibit their functions, and it gives an alarm if someone attempts to carry away the computer from a specified position without permission, thereby to prevent a theft.
Published Unexamined Patent Application No. 3-100894 discloses a technique for prohibiting unauthorized access by inhibiting key entry when a mobile terminal is stolen. If a mobile terminal is stolen, the host computer sends a predetermined signal by radio to the terminal, and in response to this, a program in the terminal operates to inhibit key entry.
As described above, a technique is known which uses an RFID tag to prevent an article from being stolen, and there are also known a technique for preventing a notebook computer from being illegally carried away from an area to be monitored, and a technique for protecting information resources by locking key entry when a computer is stolen. However, there has not been disclosed yet a technique in which an RFID tag is attached to a computer for preventing unauthorized access to the computer when it is stolen.
To prevent a theft of or unauthorized access to storage information, a device such as an RFID tag needs to be attached to a computer. On the other hand, not all users need such device, and, in general, private users need it less as compared with large-scaled corporate use. It is not preferable to sell all computers with a security function attached to it, because users who do not need it are forced to pay an extra expense. Accordingly, for computers of the same type included in a specific series, it is required that some of them have a security function and others have not.
However, for computers included in a specific series, it is preferred to share hardware and software as much as possible in the points of the sales cost and the maintenance of after-sales service. To divide the computers of a specific series into those having a security function and those having no security function when manufacturing and selling them apparently seems to make equitable the cost bearing of the users who do not need the security function, but the cost bearing increases for portions which cannot be shared, resulting in disadvantage also for such users. Thus, it is required to simultaneously solve the problems of the hardware and software sharing and the equality in the cost bearing by the user's selection of the security function.
There is a solution for this in which, if a certain security function comprises a plurality of hardware and software structural elements, some of the structural elements are made common, and the remaining part is made to be an optional component which can be added by a dealer or user at need, thereby to complete the security function. However, if the device in charge of part of the security function is attached by the user or dealer (such device is hereinafter simply referred to as security device), it is expected that such part could be illegally removed to break the security function.
Accordingly, it is an object of the present invention to provide a technique which prohibits access to a computer if a partial device in charge of the security function of the computer is removed from the computer. Further, it is another object of the present invention to provide a preferred attachment construction for a security device which is optionally attached by a user or dealer.